The technology disclosed relates to scanning of large flat substrates for reading and writing images. Examples are flat panel displays, Printed Circuit Boards (PCBs) and photovoltaic panels. Reading and writing is to be understood in a broad sense: reading may mean microscopy, inspection, metrology, spectroscopy, interferometry, scatterometry, etc. of a large workpiece, and writing may mean exposing a photoresist, annealing by optical heating, ablating, or creating any other change to the surface by an optical beam. In particular, we disclose a technology that uses a rotating or swinging arm that describes an arc across a workpiece as it scans, instead of following a traditional straight-line motion.
FIG. 1 shows one variety of prior art scanning systems. A flat workpiece 110 is placed on a stage 120 and a writing or reading head 130 is scanned across it. The stage 120 advances the workpiece 110 in one direction as the head 130 scans in a perpendicular direction. A final lens 150 may be placed between the head 130 and workpiece 110. Other systems have a stationary workpiece and a scanning head that moves along perpendicular axes, such as x-y axes. Still other systems have a stationary scanning head and a stage that moves along perpendicular axes. Each of these architectures has its own mechanical characteristics that impact its effective scanning speed.
For instance, a scanning head often needs services, such as cooling water, gas, or RF cables 132. Bending of cables and support members can impact both reliability and performance. Some serviced reading and writing heads are heavy, bulky or otherwise unsuitable for fast movements.
Systems that rely on x-y stage movement typically have heavy stages with large inertia that are very stiff to avoid sag and relatively unimpacted by outside vibrations. The heavy scanning stages require force proportional to their mass to accelerate and stop as they change direction.
Problems with writing increase as the target surfaces become larger and are made from thinner, more easily deformed materials. Larger stages require increased stiffness. More easily deformed materials require pattern manipulation from one layer to the next, on a piece by piece basis.
Accordingly, an opportunity arises to develop a new fast scanning architecture with improved throughput. A relatively low cost system with high performance may result.